Systems and methods for a rack-mounted communications switch component

ABSTRACT

A subassembly includes a plurality of card guides formed to receive card assemblies and also to conduct air for cooling purposes to improve cooling of components on the card guide. The card guides are particularly formed to place the cards in a location to facilitate airflow and to more evenly distribute the airflow. The invention further includes a method for designing the card guides to achieve the stated functionality. The method of designing the card guides includes determining a first and a second volume of space that is desired in relation to the amount of expected heat that is to be generated within the first and second volumes of space.

BACKGROUND

[0001] 1. Technical Field

[0002] The present invention relates generally to rack-mountablecommunication system housings that contain integrated circuitry and,more particularly, to the manner of construct of such communicationsystem housings.

[0003] 2. Description of the Related Art

[0004] Communication systems are well known. Communication systems haveexisted in many forms for quite some time. For example, the publicswitched telephone network (PSTN) has been in widespread use for manydecades. The PSTN is a circuit switched communication network in whichcommunications share time divided bandwidth. Such a circuit switchednetwork is contrasted to the Internet, for example, which is a packetswitched network. In packet switched networks, all communications arepacketized and transmitted in a packetized format from a source to adestination.

[0005] Communication systems include a large number of switches coupledby communication links. The switches include integrated circuitry thatperforms storage and routing functions for the communications. Thecommunication links may be physical media, e.g., optical fiber, copper,etc. The communication links may also be wireless, e.g., microwavelinks, satellites links, radio links, etc.

[0006] As communication demands have been ever increasing, the loadsplaced upon both the communication switches and the communication linkshave also increased. Thus, higher capacity switches and higher capacitycommunication links have been created to meet these demands. With thewide scale miniaturization of integrated circuits, switches can now beconstructed to provide high volume switching but be contained in arelatively small housing. Further, with the development of media such asoptical fiber, the communication links are capable of carryingsignificant levels of communications between switches.

[0007] Communication system switches, as is also well known, may behigh-speed carrier network switches that handle a huge amount of trafficor may be smaller switches, which carry lesser volumes of traffic. Theamount of traffic that can be carried by a switch depends upon not onlyupon the number and bandwidth of communication links coupled to theswitch but the processing capabilities of the switch itself. Thus, toincrease the processing capabilities of the switch, it is important toplace all components of the switch into a small area to decrease thesize of the switch.

[0008] As switches become ever smaller they experience significantoperational problems. For example, it is desirable to construct switchessuch that they have a minimum footprint size. Further, it is desirableto modularize the switches into components. Thus, most switches aretypically constructed to include a plurality of rack mounted switchcomponents/housings, each of which performs a portion of the operationsof the switch. These rack mounted switch components are placedvertically with respect to one another. Each of the switch componentscouples to physical media that forms a communication link and alsocouples to a back plane of the rack so that the switch component mayroute traffic to and from other switch components. This rack-mountedstructure therefore provides great efficiencies in reducing thefootprint size of the overall switch and also allows a number of switchcomponents to be efficiently coupled to one another. Switching functionsmay be divided between the switch components to produce greaterthroughput and for backup/fail over purposes.

[0009] However, each switch component produces a large amount of heatbecause the switch component includes a large number of integratedcircuits, each of which produces significant heat. Thus, cooling of theintegrated circuits within the switch components is a difficult task.When this task is not properly accomplished, the integrated circuits onthe switch components fail causing the overall capacity of the switch todecrease and may cause disruption in the communication path thatincludes the switch component.

[0010] A further difficulty in such a rack mounted switch configurationis that the integrated circuits themselves produce EMI. This EMI may belarge enough to interfere with other integrated circuits within theswitch components of the rack and even to cause disruption in the backplane coupling the switch components. Further, the FederalCommunications Commission limits the amount of EMI energy that may beproduced by devices of this type. Thus, it is important to either designthe switch components to minimize EMI or to provide adequate shieldingfor the switch components.

[0011] Each of the switch components physically includes a circuit boardupon which the plurality of integrated circuits is mounted. Coupled tothis printed circuit board is a physical media, e.g., optical fibermedia. Because of the space limitations for the rack mounted switchcomponents, it is desirable to minimize the overall depth of the switchcomponent. However, in conventional rack mounted switch components, theoptical fiber media is inserted perpendicular to the face of the rackmounted switch components. This type of mounting increases the depth ofthe switch component and often results in unintentional bending of, anddamage to the optical fiber media.

[0012] Additional difficulties relate to the structure of printedcircuit boards that reside within the switch components. Each switchcomponent typically includes at least one circuit board that providesthe switching functionality for the switch component. These circuitboards fit within a housing that has a predetermined size and that isreceived within a rack. Disposed on each circuit board are a pluralityof integrated circuits, termination points for physical media, and aconnector that couples the circuit board to the back plane of a rack inwhich a respective housing mounts. When any components of the circuitboard fail, the circuit board must be removed from the housing andreplaced with an operational circuit board. During this replacementoperation, the switching functionality of the circuit board is lost.Thus, redundancies are built into the circuit boards, e.g., parallelmedia connection points that couple to parallel media, that cause thecircuit board to provide its functions even when one component fails,e.g., a media coupler. However, such redundancy does not addressproblems caused by the failure of integrated circuits upon the circuitboard. In such case, the circuit board must be fully removed to replacethe circuit board with a fully functioning circuit board.

[0013] Traditional rack assemblies are made to hold rack sub-assemblieshaving a twenty-three inch form factor. Stated differently, the width ofa traditional sub-assembly is twenty-three inches in width. Lately,however, there is a trend to utilize sub-assemblies having anineteen-inch form factor. Accordingly, vendors of sub-assembliestypically make both nineteen inch and twenty-three inch sub-assemblyproducts according to the requirements of the telecommunication serviceproviders.

[0014] From the telecommunication service provider's perspective, itmust determine whether to go with a particular nineteen inch or twentythree inch sub-assembly according to a plurality of considerationsincluding available space for nineteen or twenty three inch racks and,also, the space within the racks it presently owns or plans to acquire.Thus, logistic issues and space availability considerations may oftendrive equipment purchase decisions.

[0015] Another issue relating that should be considered is thattwenty-three inch sub-assembly systems are traditionally made to conductexhaust from cooling air out of a backside of the sub-assembly. Somesub-assemblies, however, are made to conduct exhaust from cooling airout of one of its two side panels. Accordingly, a nineteen-inchsub-assembly cannot be made to merely fit within a twenty-three inchrack without violating traditional air exhaust port placement.

[0016] These shortcomings, among a great other remain unaddressed by aprior art rack mounted communication system components. Thus, there is aneed in the art for improvements in such rack mounted communicationsystem components.

SUMMARY OF THE INVENTION

[0017] The present invention provides a rack mount extension that isformed to conduct cooling air exhaust received from a nineteen-inchsub-assembly side panel to a rear exhaust port. The rack extension isformed to attach to the sub-assembly and to enable it to be installedinto a rack having a twenty-three inch form factor. Accordingly,sub-assembly vendors are not required to make sub-assemblies in twodifferent sizes. Additionally, telecommunication service providers areable to better utilize existing racks having twenty three inch formfactors in that such racks may be used in place of being forced to usenineteen inch racks for any nineteen inch sub-assemblies that areavailable or that the service provider wants to use.

[0018] Other features and advantages of the present invention willbecome apparent from the following detailed description of the inventionmade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] A better understanding of the present invention can be obtainedwhen the following detailed description of the preferred embodiment isconsidered in conjunction with the following drawings, in which:

[0020]FIG. 1 is a schematic view of a rack-mounted switch that includesa plurality of rack-mounted switch components constructed according tothe present invention;

[0021]FIG. 2 is a perspective view of a rack-mounted switch componentconstructed according to the present invention that has been removedfrom the rack of FIG. 1;

[0022]FIG. 3 is an exploded view of the rack-mounted switch component ofFIG. 2;

[0023]FIG. 4 is a sectional view of a seam of the enclosure of therack-mounted switch component of FIG. 2;

[0024]FIG. 5 is a sectional view of one embodiment of an enclosure ofthe rack-mounted switch component of FIG. 2 constructed according to thepresent invention;

[0025]FIG. 6 is a sectional view of a second embodiment of an enclosureof the rack-mounted switch component of FIG. 2 constructed according tothe present invention;

[0026]FIG. 7 is a perspective view illustrating the construction of aportion of a multi-fan module of the present invention that assists inpreventing EMI leakage from the enclosure;

[0027]FIG. 8 is a schematic view of a motherboard and two daughterboards constructed according to the present invention;

[0028]FIG. 9 is a schematic view illustrating the relative positioningof the multi-fan module, the motherboard and daughter boards of thepresent invention;

[0029]FIG. 10A is a diagrammatic sectional view showing the constructionof card guides, according to the present invention, that causes adiverted airflow;

[0030]FIG. 10B is a diagrammatic sectional view of a card guideconstructed according to the present invention;

[0031]FIGS. 11A and 11B are schematic views illustrating a mother boardand a daughter board with a reset switch constructed according to thepresent invention that may be employed to reset the components of amotherboard;

[0032]FIG. 12 is a schematic view illustrating the structure ofmotherboard and daughter board extractors constructed according to thepresent invention;

[0033]FIG. 13 is a schematic view illustrating daughter boards that areengaged within a motherboard according to the present invention;

[0034]FIG. 14 is a schematic view of the motherboard with one daughterboard removed therefrom illustrating the manner in which the daughterboard engages the motherboard;

[0035]FIG. 15A is a perspective cutaway view of a nineteen-inchsub-assembly with an attached four-inch rack-mount extension formed toconduct exhaust from a rear side according to one embodiment of thepresent invention;

[0036]FIG. 15B is a perspective view of a four-inch rack-mount extensionillustrating air inlet and exhaust ports;

[0037]FIG. 15C is a perspective view of a four-inch rack-mount extensionillustrating the closed sides having a plurality of embossments forreceiving mounting hardware and further illustrating that the extensionis formed to also be a duct for exhaust air according to one embodimentof the described embodiment;

[0038]FIG. 16 is a perspective view of a fan tray formed to receive andhold a plurality of fans for cooling a sub-assembly;

[0039]FIG. 17 is a schematic view of a multi-fan module constructedaccording to the present invention;

[0040]FIG. 18 is a schematic view of a fan constructed according to thepresent invention;

[0041]FIG. 19 is a schematic top view of a multi-fan module constructedaccording to the present invention with fans partially removedtherefrom;

[0042]FIG. 20 is a schematic side view of a multi-fan module constructedaccording to the present invention;

[0043]FIG. 21 is a schematic view of a prior art technique for couplingoptical fiber media to a printed circuit board;

[0044]FIG. 22 is a schematic view of a daughter board constructedaccording to the present invention in which optical fiber media couplesto the daughter board substantially parallel to a front edge of thedaughter board;

[0045]FIG. 23 is another view of a daughter board constructed accordingto the present invention showing the manner in which optical fiber mediacouples to the daughter board;

[0046]FIG. 24 is a diagrammatic top view of a daughter board constructedaccording to the present invention showing the manner in which opticalfiber media couples to the daughter board;

[0047]FIG. 25 is a logic diagram illustrating a method for inserting afan into the multi-fan tray according to the present invention;

[0048]FIG. 26 is a logic diagram illustrating a method installing anoptical fiber media onto a printed circuit board according to thepresent invention; and

[0049]FIG. 27 is a logic diagram illustrating a method for constructinga card guide according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a schematic view of a rack-mounted switch 100 thatincludes a plurality of rack-mounted switch components 102A through 102Iconstructed according to the present invention. Each of the 19-inchrack-mounted switch components must fit within a space having a maximumdimension of 17.72 inches wide, 12 inches deep and 1¾ inches in height.These dimensions are substantially standardized within the industriesfor rack-mountable communications and for other communication systemrack-mounted equipment. Thus, each rack-mounted switch componentincludes a housing that contains the other parts of the rack-mountedswitch components and, at the same time, conforms to the sizelimitations.

[0051] The rack includes side supports 106 to which the switchcomponents 102A-102I attach. Further, the rack also includes back planeconnections to allow the switch components 102A-102I to communicativelyintercouple with one another. Such a rack structure is generally knownin the art and will not be described further herein except as to expandupon the principles of the present invention.

[0052] As is shown, physical media 104A-104I extends switch components102A-102I, respectively. According to one embodiment of the enclosure ofthe present invention, the physical media 104A-104I are optical fibermedia that exit the enclosure in a direction substantially parallel to afront surface of the switch components 102A-102I housings. By having themedia extend in such a direction, with respect to the switch components102A-102I housings and the rack 100 in which the switch components102A-102I mount, a lesser depth for the combination of the switchcomponents 102A-102I and the physical media 104A-104I results. Ininstallations in which floor space and access space is limited, thisreduction in depth greatly simplifies the installation of the rack 100.

[0053]FIG. 2 is a perspective view of a rack-mounted switch componentaccording to the present invention that has been removed from the rackof FIG. 1. An external portion of the rack-mounted switch component isreferred to as an “enclosure” 200. The enclosure 200 is formed of metaland substantially surrounds all components contained therein. As will bedescribed further with respect to FIG. 3 and subsequent figures,contained within the enclosure 200 are circuit boards, which contain aplurality of integrated circuits, interconnections for the circuitboard, cooling fan structure and connection structures for the physicalmedia.

[0054] The enclosure 200 includes a metal shell 202 that is formed froma plurality of pieces. The manner in which the metal shell of theenclosure is formed will be described further with reference to FIGS. 4,5 and 6. The enclosure 200 also includes rack-mounting brackets 204A and204B for securing the enclosure 200 within the rack as was illustratedin FIG. 1.

[0055]FIG. 3 is an exploded view of the rack-mounted switch component ofFIG. 2. As is shown, a rack-mounted switch component 300 includes anenclosure having a system case that includes a first portion 302A and asecond portion 302B. The enclosure also includes a front panel 304 and aback panel 306. Contained within the enclosure are a multi-fan module308, a first motherboard/daughter board combination 310, and a secondmotherboard/daughter board combination 312. The motherboard and daughterboard combinations 310 and 312 are received within the enclosure duringnormal operation. The back panel 306 of the enclosure includes a backplane connector 314 to which the motherboard/daughter board combinations310 and 312 connect.

[0056]FIG. 4 is a sectional view of a seam of the enclosure of therack-mounted switch component of FIG. 2. As shown in FIG. 4, anoverlapping seam 402 joins two metal sections 404 and 406 of theenclosure. These two metal sections 404 and 406 may be two of the systemcase and the front panel, the system case and the back panel, or anyother two components of the enclosure. As is shown, this overlappingseam structure 402 eliminates a line of sight from within the enclosureexternal to the enclosure. Therefore, the seam 402 prevents internallygenerated electromagnetic radiation interference (EMI) from escaping theenclosure along the seam 402. As is generally known, integrated circuitsoperating at high switching frequencies generate EMI energy. If this EMIenergy escapes the enclosure, it would be EMI that would interfere withoperation of other integrated circuits. Thus, the seam structure 402illustrated in FIG. 4 provides significant shielding for thosecomponents contained within the enclosure and also prevents thosecomponents within the enclosure from causing interference with othercomponents external to the enclosure.

[0057] An additional benefit of the seam structure 402 of FIG. 4 is thatit allows the enclosures of the present invention to be constructed withminimal welding. As is generally known, in forming EMI shieldedenclosures of metal, it is typical to weld each and every seam of theenclosure fully along the length of the seam. This welding is expensiveand delays the construction of the enclosures. The seam 402, as shown inFIG. 4, allows enclosures to be constructed with minimal spot welds orfasteners while still providing superior EMI shielding.

[0058]FIG. 5 is a sectional view of one embodiment of an enclosure 500of the rack-mounted switch component of FIG. 2 constructed according tothe present invention. The enclosure is constructed to include threevolumes. A first volume 502 is constructed to accept a multi-fan module.The multi-fan module produces an airflow that passes across the surfacesof two motherboard/daughter board combinations that are received withina second volume 504 of the enclosure. A third volume 506 serves as aplenum area to allow air that has been heated, via passing across themotherboard/daughter board combinations, to exit the enclosure.

[0059] In this embodiment, the system case is formed of a first portion508 and a second portion 510 that are joined using the joints 402illustrated in FIG. 4. The first portion 508 and second portion 510 ofthe system case define the third volume 506. Another component 512 ofthe enclosure serves to segregate the first volume 502 from the secondvolume 504. The component 512 also provides support for a pair of tracks514 and 516 that will act as the card guides of the motherboard/daughterboard combinations 310 and 312 (of FIG. 3). The structure 512 isperforated to allow air created by the multi-fan modules to pass fromthe first volume 502 into the second volume 504 that receives themotherboard/daughter board combinations. The first portion 510 of thesystem case also includes a component 522 that segregates the secondvolume 504 from the third volume 506. This component 522 supports a pairof tracks 518 and 520 that will receive card guides of themotherboard/daughter board combinations. This component 522 of the firstportion 510 of the system case also includes perforations that allowheated cooling air to pass from the second volume 504 to the thirdvolume 506. This heated air is vented from the third volume 506 to exitthe enclosure of the system component. Thus, as with the structure ofFIG. 5, the enclosure may be constructed fairly simply from pre-formedmetal sheeting with minimal welds required and provide significant EMIshielding.

[0060]FIG. 6 is a sectional view of a second embodiment of an enclosureof the rack-mounted switch component of FIG. 2 constructed according tothe present invention. The second embodiment of the enclosure includes afirst volume 602 for receiving a multi-fan module, a second volume 604for receiving the pair of motherboard/daughter board combinations, and athird volume 606 that serves as a plenum. The system case includes twocomponents 608 and 610 that are preformed of metal. These components 608and 610 are joined, via the joint structure 402 of FIG. 4, to providesuperior EMI shielding. Component 610 also includes tracks 612, 614, 616and 618 that receive the motherboard/daughter board combinations withinvolume 604. Perforated portions 620 and 622 of component 610 allowcooling air to flow from the first volume 602 to the second volume 604,and from the second volume 604 to the third volume 606, respectively.

[0061]FIG. 7 is a perspective view illustrating the construction of aportion of a multi-fan module of the present invention that assists inpreventing EMI leakage from the enclosure. The multi-fan module resideswithin the first volume (e.g., the first volume 502 of FIG. 5 and thefirst volume 602 of FIG. 6) of a housing that is constructed to minimizeEMI leakage. Because the multi-fan module must have a substantiallyuninhibited opening external to the enclosure so that it may receivecool air for cooling the motherboard/daughter board combinations, itmust avoid having a line of sight path external to the enclosure. Thus,the structure of this portion of the multi-fan module includes a frontpanel 702, a top panel 704, and a bottom panel 706. Also included is anopening 708 that allows air to be drawn into the multi-fan module fromexternal in to the enclosure. An inner panel 718 joins top panel 704 andbottom panel 706 and helps prevent EMI leakage through opening 708.

[0062] Curved surfaces 710 and 712 formed in bottom panel 706 and toppanel 704, respectively, serve to reduce/preclude EMI leakage throughopening 708. In particular, curved surfaces 710 and 712, in combinationwith front panel 702 and inner panel 714, provide a trapping mechanismfor internally produced EMI. Thus, free airflow may pass through opening708 and along a surface 718 of panel 714 into the multi-fan module forcooling the motherboard/daughter board combinations.

[0063]FIG. 8 is a schematic view of a motherboard and two daughterboards constructed according to the present invention. As shown in FIG.8, a motherboard/daughter board combination 800 includes a motherboard802, a daughter board 804, and a daughter board 806. Contained upon bothsurfaces of motherboard 802 are integrated circuits. These integratedcircuits may be mounted to motherboard 802 via hole connections orsurface mount connections. The manner in which integrated circuits areaffixed to circuit boards is generally known and will not be discussedfurther herein except as to expand upon the teachings of the presentinvention.

[0064] Integrated circuit components and media connectors are affixed toboth surfaces of daughter boards 804 and 806. The structure of circuitboards that include media connectors and integrated circuits is alsoknown and will not be described further except as to expand upon theteachings of the present invention. Fixed to the motherboard 802 is apair of card guides 808 and 810. These card guides 808 and 810 matinglyengage a pair of tracks (e.g., tracks 612 and 616 of FIG. 6) containedwithin an enclosure. With the motherboard fully engaged within theenclosure, a back plane connector 812 fixed to the motherboard 802couples to a back plane connector contained within the enclosure. Inthis fashion, the motherboard 802 may communicate with other devicescoupled to the back plane connector of a rack in which the enclosuremounts via the back plane connector of the enclosure.

[0065] Each of the daughter boards 804 and 806 matingly engages with themotherboard 802 via connectors. For example, daughter board 804 includesa connector 818, which engages a connector 816 of motherboard 802.Likewise, daughter board 806 includes a connector 820, which engages aconnector 814 of motherboard 802. The manner in which the daughterboards 804 and 806 couple to the motherboard 802 is in a co-planerfashion. In this co-planer fashion, daughter boards 804 and 806 residein substantially the same plane as the motherboard 802. By having thisco-planer connection, the daughter boards 804 and 806 may be removedfrom the motherboard 802 without removing the motherboard 802 from theenclosure. This provides significant benefits in replacing daughterboards that have failed components without disabling the operation ofthe motherboard. For example, in one embodiment, daughter boards 804 and806 provide redundancy in communication paths provided by coupled media.If one of the daughter boards fails, e.g., daughter board 804, thefailed daughter board 804 may be separated from the motherboard 802without disabling the other daughter board 806 or the motherboard 802.

[0066] To support this co-planer functionality, the latching mechanismwith which the daughter boards 804 and 806 couple to the motherboard 802and the manner in which the motherboard 802 couples to the enclosure isa significant improvement over prior devices. The latching structurethat latches the motherboard 802 to the enclosure includes a firstextractor 822 and a second extractor 824. These extractors 822 and 824couple to the card guides 808 and 810, respectively, and may only bedisengaged from the enclosure when the daughter boards 804 and 806 aredisengaged from the motherboard 802. Extractors 828 and 830 couple thedaughter board 806 to the motherboard 802. Further, extractors 832 and834 couple the daughter board 804 to the motherboard 802. Extractors 828and 834 are constructed to be coexistent with extractors 822 and 824,respectively.

[0067]FIG. 9 is a schematic view illustrating the relative positioningof the multi-fan module, the motherboard and daughter boards of thepresent invention. As shown in FIG. 9, a multi-fan module 900 residesadjacent a motherboard 902. Connected to motherboard 902 are daughterboards 904 and 906. As was previously described, the multi-fan module900 produces an airflow that is directed across the upper and lowersurfaces of the motherboard 902 and the upper and lower surfaces ofdaughter boards 904 and 906 to cool the integrated circuit componentsdisposed thereon. FIG. 9 also shows faceplates 908 and 910 disposed upondaughter boards 904 and 906, respectively. These faceplates 908 and 910assist in preventing EMI produced by the components of motherboard 902and daughter boards 904 and 906 from escaping the enclosure.

[0068]FIG. 10A is a diagrammatic sectional view showing the constructionof card guides according to the present invention that causes a divertedairflow. As shown in FIG. 10, the multi-fan module produces an airflow1002 that passes through a dividing wall 1004 having airflow openingsthereupon. The airflow 1002 enters a second volume of the enclosure inwhich motherboards 1010 and 1012 (and coupled daughter boards) arecontained. Fixed to the dividing wall 1004 are tracks 1014 and 1016 thatreceive card guides 1014 and 1016.

[0069] Contained upon the motherboards 1010 and 1012 are integratedcircuits (ICs). These integrated circuits are contained on both surfacesof the motherboards 1010 and 1012. As is known, integrated circuitcomponents generate substantial amounts of heat that must be removedfrom the integrated circuits to prevent the integrated circuits fromover-heating and failing. Thus, the airflow 1012 passes across thesurfaces of the motherboards 1010 and 1012 to remove the heat generatedby the integrated circuits. According to the present invention, cardguides 1014 and 1016 are designed to control the volume of airflow 1002so that it advantageously and effectively cools all integrated circuitscontained upon the motherboards 1010 and 1012.

[0070]FIG. 10B is a diagrammatic sectional view of a card guideconstructed according to the present invention. Referring now to FIG.10B, the elongated guide includes a first portion 1050 that slidinglyengages the track 1008 and a second portion 1052 that is affixed to themotherboard 1010. As is shown, the second portion 1052 of the elongatedguide 1014 is offset from the first portion 1050 of the elongated guide.Such offset of the first portion 1050 to the second portion 1052 altersthe airflow 1002 applied to a bottom surface of the circuit board 1054and to a top surface 1056 of the motherboard 1010. The structure of theelongated guides 1014 and 1016 are designed to correctly divertappropriate portions of the airflow 1002 to the various surfaces of themotherboards 1010 and 1012.

[0071] Referring again to FIG. 10A, the second volume within theenclosure occupied by the motherboards/daughter boards 1010 and 1012,may be subdivided into 3 particular sub volumes. A distance 1018, thatis, the distance between the top inner surface of the enclosure 1000 andan upper surface of motherboard 1010, corresponds to a first sub volume1030. A second distance 1020 is the distance between a lower surface ofthe upper motherboard 1010 and an upper surface of the lower motherboard1012 and corresponds to a second sub volume 1032. A third distance,distance 1022, is the distance between an inner surface of the lowerside of the enclosure 1000 and the lower surface of motherboard 1012 andcorresponds to a third sub volume 1034.

[0072] According to the present invention, integrated circuitry is laidout on both sides of the motherboards 1010 and 1012. Further, integratedcircuitry is also laid out on daughter boards that couple to themotherboards. These daughter boards are not shown in the sectional viewof FIG. 10A but their structure will be apparent to the reader fromviewing the other drawings. Each of the integrated circuits contained onthe surfaces of the motherboards 1010 and 1012, as well as the daughterboards, generates heat. Because the motherboards 1010 and 1012, as wellas the daughter boards, are good thermal insulators, the heat generatedin each of the sub volumes 1030, 1032 and 1034 must be removed in adirection parallel to the surfaces of the motherboards 1012 and 1010.Since the total cooling provided by the airflow 1002 is known, the cardguides 1014 and 1016 have offsets to divert airflow based upon the heatthat is generated within each of the volumes 1030, 1032, and 1034.

[0073] Given that a particular airflow volume 1002 is sufficient to coolall integrated circuits contained within sub volumes 1030, 1032, and1034, the offsets are determined to produce optimum cooling. Integratedcircuits that are more temperature sensitive, i.e., that cannot beoperated at higher temperatures, are placed on the motherboards 1010,1012 and the daughter boards to be closer to the multi-fan module suchthat they receive a larger cooling airflow. Further, integrated circuitsthat produce higher levels of heat and/or are less temperature sensitivemay be placed on portions of the motherboards 1010 and 1012 farther fromthe multi-fan module.

[0074]FIGS. 11A and 11B are schematic views illustrating a motherboardand a daughter board with a reset switch constructed according to thepresent invention that may be employed to reset the components of amotherboard. A motherboard 1100 couples to daughter boards 1102 and1104. However, the components of the motherboard 1100 are not accessibledirectly without removing the daughter boards 1102 and 1104 from themotherboard 1100. Thus, a card guide 1108 includes a reset switch 1110that moves within the card guide 1108 and couples to a reset device1106. This reset device 1106, when activated via the reset switch 1110,causes the motherboard 1100 to enter a reset mode. Thus, when themotherboard 1100 enters an inoperative state, it may be reset withoutremoving daughter boards 1102 and 1104 from the motherboard 1100 andfrom the housing.

[0075]FIG. 12 is a schematic view illustrating the structure ofmotherboard and daughter board extractors constructed according to thepresent invention. As shown in FIG. 12, a daughter board 1202 includesextractors 1204 and 1206. Extractor 1204 engages an extraction surfacefixed to the daughter board 1202. A motherboard extractor 1210 pivotallyattaches to a first portion 1212 of a card guide 1216 and engages theenclosure (not shown). Further, extractor 1206 engages an extractionsurface 1208 fixed to a second portion 1214 of the card guide 1216.

[0076] In the illustrated embodiment, each of the extractors 1204 and1206, and motherboard extractor 1210 includes an actuator and anextraction surface. A person uses respective actuators to move theextractors 1204 and 1206, and motherboard extractor 1210 between engagedpositions and released positions. However, it may be advantageous tofurther prevent unintentional actuation of the motherboard extractor1210. Thus, in another embodiment, the motherboard extractor 1210 doesnot include an actuator that may be grasped, but, instead, includes aslot that receives a screwdriver or a similar tool, with such toolrequired to move the motherboard extractor 1210 from an engaged positionto a released position. In this fashion, the motherboard extractor 1210cannot be disengaged from the enclosure without the use of a tool. As isevident, the use of extractors 1204 and 1206 allow the daughter board1202 to be disengaged from a motherboard 1220.

[0077]FIG. 13 is a schematic view illustrating daughter boards that areengaged within a motherboard according to the present invention. Theview of FIG. 13 shows a motherboard 1300 with which daughter boards 1302and 1304 are matingly engaged. Extractors 1306 and 1308 are used toengage and remove the motherboard 1300 from an enclosure. Extractor 1306is shown in an engaged position even though the motherboard 1300 isremoved from the enclosure. Extractors 1306 and 1308 are shown in areleased position.

[0078] Daughter board 1302 includes extractors 1310 and 1312. Daughterboard 1304 includes extractors 1314 and 1316. Each of the extractors1310, 1312, 1314, and 1316 is in the engaged position. As is shown, thedaughter board extractors 1310, 1312, 1314, and 1316 are in the engagedposition and their front edges are flush with the front edge ofmotherboard 1300, as well as with the front edge of motherboardextractor 1306 that is in the engaged position. Further, the extractorsin the engaged position are also flush with faceplates 1320 and 1322 ofdaughter boards 1302 and 1304, respectively. The flush alignment of eachof these components not only reduces the depth of the combination of themotherboard 1300 and daughter boards 1302 and 1304, but also assists inpreventing EMI generated by the motherboard 1300 and daughter boards1302 and 1304 from escaping from an enclosure in which these componentsare contained.

[0079]FIG. 14 is a schematic view of the motherboard with one daughterboard removed therefrom illustrating the manner in which the daughterboard engages the motherboard. As shown in FIG. 14, a motherboard 1300and a daughter board 1302 are matingly engaged. In this engagedposition, daughter board extractors 1310 and 1312 are in their engagedpositions engaging extraction surfaces 1402 and 1404, respectively. Aswas previously described, extraction surface 1402 is fixed to the secondportion of the elongated guide. However, extraction surface 1404 isfixed to a daughter board track 1406, which, in turn, is fixed tomotherboard 1300. As is also shown in FIG. 14, extraction surface 1408is also affixed to the daughter board track 1406. The other daughterboard 1304 (not shown) uses this extraction surface 1408 when matinglyengaging the motherboard 1300.

[0080]FIG. 15A is a perspective cutaway view of a nineteen-inchsub-assembly with an attached four-inch rack-mount extension formed toconduct exhaust from a rear side according to one embodiment of thepresent invention. As may be seen, a sub-assembly seen generally at 1500is attached to a four-inch rack-mount extension shown generally at 1504.At an end opposite of the extension 1504, sub-assembly 1500 includes anarea 1508 for receiving a fan tray.

[0081] A front side of sub-assembly 1500 includes an inlet port showngenerally at 1512 for receiving air that is propelled through thesub-assembly 1500 by the fans of a fan tray once a fan tray isinstalled. As may also be seen, extension 1504 includes a bracket 1516that is attached thereto to enable sub-assembly 1500 to be mountedwithin a rack having a twenty-three-inch form factor.

[0082] In operation, the fans of the fan tray draw air into thesub-assembly 1500 in direction 1520 through inlet port 1512. The airdrawn in through inlet port 1512 is then propelled in a generally axialdirection shown generally at 1524. The air is exhausted fromsub-assembly 1500 through at least one exhaust port 1528. The extension1504 then receives the exhaust through an inlet port shown generally at1532 and conducts the air towards a rear exhaust port 1534 of theextension 1504 as is shown at 1536. The exhaust air is then expelledfrom the extension 1504 in a direction 1540 through extension 1504 rearexhaust port 1534. As may be seen in this diagram and with a comparisonof the arrangement of the fiber optic couplers, the fiber opticcouplers, when installed, are axially aligned with the airflow withinthe sub-assembly 1500 in axial direction 1524. Moreover, a “front door”shown generally at 1544 is shown from which fiber optic fibers extendfrom the sub-assembly 1500.

[0083] In the described embodiment of the invention, the sub-assembly1500 is formed of 18-gauge metal (0.048 inches thick) while theextension 1504 is formed of 16-gauge metal (0.060 inches thick).Additionally, extension 1504 forms openings sufficiently large enough toenable a tightening tool, such as an Allen wrench or a screwdriver, tobe inserted therein to tighten screws that are used to firmly secure theextension to the sub-assembly 1500. Here, in the described embodiment,#8 captive screws with 32 threads per inch are used because they serveto easily and firmly attach the extension 1504 to the sub-assembly 1500.Alternate screws and methods for attaching the extension 1504 may alsobe used. One reason the extension 1504 is formed of 16-gauge steel is toprovide adequate strength of the extension put in a high shock andvibration environment.

[0084]FIG. 15B is a perspective view of a four-inch rack-mount extensionillustrating air inlet and exhaust ports. In the described embodiment ofthe invention, extension 1504 includes substantially closed top, bottomand sides, except for screw holes and air inlet and exhaust ports.Accordingly, extension 1504 is formed to not only be an extension toenable a nineteen-inch sub-assembly to be inserted into a rack having atwenty-three-inch form factor, but is also formed to be a duct to directexhaust air that is expelled from a side of a sub-assembly towards arear of a rack.

[0085] Sub-assembly extension 1504 forms an air inlet, shown generallyat 1548, for receiving exhaust air from the sub-assembly and an airexhaust port, shown generally at 1552, through which exhaust air isexpelled. As may also be seen, extension 1504 forms a plurality ofmounting flanges 1556 for attaching the extension 1504 to asub-assembly. Finally, a plurality of apertures 1560 through which atightening tool, such as a screwdriver or Allen wrench, may be insertedto tighten captive panel screws that are attached at the apertures shownat 1564. While some exhaust air will escape from the apertures 1560 ofextension 1504 for the tightening tool, most of the exhaust air will beexpelled through exhaust port 1552.

[0086]FIG. 15C is a perspective view of a four-inch rack-mount extensionillustrating the closed sides having a plurality of embossments forreceiving mounting hardware and further illustrating that the extensionis formed to also be a duct for exhaust air according to one embodimentof the described embodiment. Extension 1504 includes a closed end 1568and a substantially closed side 1570. Substantially closed side 1570includes apertures 1560 for receiving a tightening tool. Substantiallyclosed side 1570 further includes a plurality of embossments showngenerally at 1572 for receiving mounting hardware for attaching asub-assembly 1500 with extension 1504 to a rack with a twenty-three-inchform factor. Embossments 1572 are formed to mate with and receive themounting hardware 1516 of FIG. 15A.

[0087]FIG. 16 is a perspective view of a fan tray formed to receive andhold a plurality of fans for cooling a sub-assembly. Fan tray 1600includes an inlet port 1602 that is similar to inlet port 1512 of FIG.15A. A plurality of removable fans shown generally at 1604 is formed tohave support flanges 1608 formed at the inlet and exhaust ends of theremovable fans 1604. Support flanges 1608 are formed to providestructural rigidity to the fan and to be large enough to form mountingsurfaces that are used to attach the fan to the fan tray 1600. In thedescribed embodiment, support flanges 1608 further form apertures 1612through which a mounting screw may be inserted. Additionally, in thedescribed embodiment of the invention, support flanges 1608 are alsoformed to facilitate being riveted to the fan tray 1600 in the areagenerally formed at 1616. As may be seen, fan tray 1600 is formed toreceive six fans. In addition to the two fans 1604 shown in FIG. 16,four fan-receiving stations 1620 are shown. Each of the installed fansreceives inlet air that enters the fan tray through inlet port 1602 andexpels the air in direction 1624 to cool circuit components of thesub-assembly.

[0088]FIG. 17 is a schematic view of a multi-fan module constructedaccording to the present invention. The multi-fan module 1700 includes aplurality of fans 1702A through 1702E. The multi-fan module 1700includes a front edge 1704 that has a plurality of front airflowapertures 1706A through 1706E. The plurality of fans 1702A through 1702Ereceive air via the front airflow apertures 1706A through 1706E. Themulti-fan module also includes a bottom surface 1708 that verticallylimits the engaged position of the plurality of fans 1706A through 1706Eand a back surface 1710 that includes a plurality of back airflowapertures.

[0089] The multi-fan module 1700 also includes a top surface 1712 thatcooperates with the enclosure to provide an air plenum opening throughwhich air is received into the fans 1702A through 1702E. According tothe operation of the multi-fan module 1700, air is received through theplurality of front airflow apertures 1706A through 1706E and producedfrom the back airflow apertures (not shown). The back airflow aperturesreside adjacent the enclosure volume within which themotherboard/daughter board combinations reside.

[0090]FIG. 18 is a schematic view of a fan constructed according to thepresent invention. A fan 1800 includes a fan motor 1802, a plurality offan blades 1804 coupled to the fan motor 1802, and a fan housing 1806that houses the fan motor 1802 and the plurality of fan blades 1804. Thefan 1800 also includes wiring 1808, which is attached to an externalpower source to power the fan motor 1802. The fan housing 1806 includesa flange 1810 located at one end of the fan housing 1806. This flange1810 is received by fingers formed in the front edge of the multi-fanmodule to hold the fan 1800 in place within the multi-fan module.

[0091]FIG. 19 is a schematic top view of a multi-fan module constructedaccording to the present invention with fans partially removedtherefrom. As shown in FIG. 19, the multifan module 1900 includes a topsurface 1904, a front edge 1908, and a back surface 1912. As is shown,front airflow apertures 1916A and 1916B (as well as the other frontairflow apertures) includes 2 fingers for holding the flange of a fanmotor. In particular, front airflow aperture 1916A includes fingers 1918and 1922. Further, front airflow aperture 1916B includes fingers 1926and 1930. When corresponding fans are inserted in these positions, thefingers will receive the flanges of corresponding fan housings.

[0092] The back surface 1912 includes a plurality of back airflowapertures 1934A and 1934B that proximately limit backflow of air aboutthe fan housings that couple to the corresponding front airflowapertures. For example, back surface 1912 includes back airflowapertures 1934A and 1934B that correspond to front airflow apertures1916A and 1916B, respectively. When a fan matingly engages fingers,e.g., fingers 1918 and 1922 corresponding to front airflow aperture1916A, and the fan moves against a bottom surface 1938, the back surface1912 and, in particular, the back airflow aperture 1934A, engages thehousing of the corresponding fan. In such case, this back airflowaperture 1934A limits the backflow of air about the sides of the fan.

[0093]FIG. 20 is a schematic side view of a multi-fan module constructedaccording to the present invention. FIG. 20 provides additional detailfrom a different view of the fan assembly according to the presentinvention. In particular, a front airflow aperture 1916A is open fromthe view of FIG. 20. In such case, a back airflow aperture 1934A isevident as is back airflow aperture 1934B corresponding to front airflowaperture 1916B. Fingers 1906 and 1904 corresponding to front airflowaperture 1918 are shown to be formed in a front edge 1908 of the fanassembly.

[0094]FIG. 21 is a schematic view of a prior art technique for couplingoptical fiber media to a printed circuit board. FIG. 21 illustrates acircuit board 2100. Mounted upon circuit board 2100 are a plurality ofoptical fiber couplers 2102A, 2102B, 2102C, and 2102D, each of whichreceives a pair of optical fiber media. As is shown, the optical fibermedia are received by the optical fiber couplers 2102A, 2102B, 2102C,and 2102D in a direction that is substantially perpendicular to a frontedge 2108 of the circuit board 2100. The front edge 2108 of the circuitboard 2100 is oriented such that when the circuit board 2100 is receivedwithin an opening, the front edge 2108 will be substantially parallel tothe housing opening through which the circuit board 2100 is received.

[0095] Thus, with this orientation, the optical fiber media 2104A,2104B, 2106A and 2106B are received within the optical fiber mediacoupler 2102 well away from the front edge 2108 of the integratedcircuit board 2100. Such is the case because sufficient distance mustremain between the optical fiber media couplers 2102A-2102D and thefront edge 2108 of the circuit board 2100 so that the optical fibermedia may be directed and extended from the housing in a directionsubstantially parallel to the front edge 2108 of the circuit board 2100.However, because a minimum bend radius is required so as not to damagethe optical fiber media, the media couples 2102A-2102D must be set backa minimum distance from the front edge 2108 of the circuit board 2100.In the prior art embodiment of FIG. 21, therefore, the limitationsinvolving the placement of the optical fiber media coupler resulted inwasted space on the integrated circuit board 2100.

[0096]FIG. 22 is a schematic view of a daughter board constructedaccording to the present invention in which optical fiber media couplesto the daughter board substantially parallel to a front edge of thedaughter board. As shown in FIG. 22, a daughter board 2202 includes afaceplate 2204 fixed to, and parallel with, a front edge of the daughterboard 2202. When engaged within the enclosure or another housing, thefront edge of the daughter board 2202 will be substantially parallel toa surface of the front panel of the enclosure.

[0097] Fixed to the daughter board 2202 is an optical fiber mediacoupler 2206. The optical fiber media is disposed parallel to the frontedge of the daughter board 2202 such that optical fiber media 2208 isreceived in a direction substantially parallel to a housing opening inwhich the daughter board 2202 is installed.

[0098] The daughter board 2202 also includes optical fiber media guides2210 and 2212 installed on the daughter board 2202. The optical fibermedia guide 2210 and 2212 each have a radius about which the opticalfiber media 2208 are routed so that the optical fiber media 2208 extendfrom an opening 2214 in a direction that is substantially parallel tothe housing opening. In this fashion, the optical fiber media 2208 and2210 form a semi-circle with the minimum radius about the optical fibermedia guide 2210. The radius of the optical fiber media guide 2210 isone which allows the media to be bent about the guide without damage.

[0099] Significantly, the daughter board 2202 may be constructed with aminimum depth that is sufficient to contain the optical fiber mediacoupler 2206. With the minimum depth, the daughter board 2202 uses aminimal depth of the available depth within the housing for the requiredintegrated circuitry, i.e., the motherboard.

[0100]FIG. 23 is another view of a daughter board constructed accordingto the present invention showing the manner in which optical fiber mediacouples to the daughter board. As shown in FIG. 23, a daughter board2202 includes an optical fiber media coupler 2302 that is mountedparallel to, but in an opposite direction, as compared to the opticalfiber media coupler 2206 of FIG. 22. The daughter board 2202 includesthe disposed optical fiber media guides 2210 and 2212 that were shown ondaughter board 2202 of FIG. 22.

[0101] In the structure shown in FIG. 23, the optical fiber mediacoupler 2302 receives optical fiber media 2308. The optical fiber media2308 is routed about the second optical fiber media guide 2212 and alsoabout the optical fiber media guide 2210, such that the optical fibermedia 2308 extends through the opening 2214 in the same direction asoptical fiber media 2208 extends from the opening 2214 in FIG. 22.

[0102]FIG. 24 is a diagrammatic top view of a daughter board constructedaccording to the present invention showing the manner in which aplurality of optical fiber media couple to the daughter board. As shown,four optical fiber media couplers 2206, 2302, 2402, and 2404 are mountedupon a daughter board 2202. Optical fiber media 2208, 2308, 2408, and2412 (each of which includes two optical fiber cables) couple to opticalfiber media couplers 2206, 2302, 2402, and 2404, respectively.

[0103] As is shown, optical fiber media coupler 2206 couples to asurface of the daughter board that receives optical fiber media 2208 ina first direction that is parallel to the front edge of the daughterboard. Further, optical fiber media coupler 2402 also couples to thesurface of the daughter board and receives optical fiber media 2408 inthe first direction. Optical fiber media couplers 2302 and 2404 coupleto the surface of the circuit board and receive optical fiber media 2308and 2412, respectively, in a second direction that is substantiallyparallel to, but opposite, the first direction.

[0104] Optical fiber media guide 2212 couples to the surface of thedaughter board and tangentially receives optical fiber media 2308 and2412. Optical fiber media guide 2212 provides a routing path for theoptical fiber media 2308 and 2412 in the manner shown. As illustrated,the optical fiber media guide 2212 includes an opening 2406 throughwhich optical fiber media 2308 and 2412 are received. Thus, the opticalfiber media guide 2212 provides different routing paths for opticalfiber media 2308 and optical fiber media 2412.

[0105] Optical fiber media guide 2210 also tangentially receives opticalfiber media 2308 and 2412 and provides a routing path for the opticalfiber media 2308 and 2412. Optical fiber media guide 2210 alsotangentially receives optical fiber media 2208 and 2408 and provides arouting path for the optical fiber media 2208 and 2408. In combination,the optical fiber media guides 2210 and 2212 provide routing paths sothat the optical fiber media extend from the daughter board and ahousing opening adjacent the front edge of the daughter boardsubstantially parallel and in the same direction to the front edge ofthe daughter board. The routing paths provided prevent the optical fibermedia 2208, 2308, 2408, and 2412 from being bent at a radius less thanthat provided by the optical fiber media guides 2210 and 2304.

[0106]FIG. 25 is a logic diagram illustrating a method for inserting afan into the multi-fan tray according to the present invention. Themethod requires first unlatching the multifan tray from an enclosurehousing the multifan tray (step 2502). Then, the multifan tray isremoved from the enclosure (step 2504). Next, the power supply isdisconnected from a failed fan of a plurality of fans held by themultifan tray (step 2506). The failed fan is extracted from the multifantray by lifting the fan to remove a flange of the fan from a pluralityof fingers formed in the multifan tray that slidingly engage the flange(step 2508).

[0107] With the failed fan removed, a new fan is inserted into themultifan tray by engaging a flange of the fan into the plurality offingers formed in the multifan tray (step 2510). The new fan is thenconnected to the power supply (step 2512). Then, the multifan tray isinserted into the enclosure (step 2514). Finally, the multifan tray islatched into the enclosure (step 2516).

[0108]FIG. 26 is a logic diagram illustrating a method installing anoptical fiber media onto a printed circuit board according to thepresent invention. According to this operation, an end of an opticalfiber optic media is inserted into an optical fiber media coupler thatresides in a substantially parallel orientation relative to a front edgeof the printed circuit board (2602). Then, the optical fiber media isrouted about a radial surface of an optical fiber media guide (step2604). Finally, the optical fiber media is extended through a mediaegress aperture in a substantially parallel direction with respect tothe media egress aperture (step 2606). The media egress aperture isreferred to as 2214 in FIG. 22.

[0109]FIG. 27 is a logic diagram illustrating a method for constructinga card guide according to the present invention. According to thismethod, a pair of elongated guides are designed that affix to a circuitboard and that allow the circuit board to be slidingly engaged within anenclosure. Within the enclosure is produced a cooling airflow and theenclosure includes a pair of slots that receive the pair of elongatedguides. The method commences by determining a division of the coolingairflow volume within the enclosure by the location of the pair of slotassemblies (step 2702).

[0110] The method then proceeds with determining a first heating amountproduced by a first plurality of components residing upon a firstsurface of the circuit board (step 2704). Then, a second heating amountproduced by a second plurality of components residing upon a secondsurface of the circuit board is determined (step 2706). Finally, anoffset of second portions of the elongated guides from first portions ofthe elongated guides is determined to selectively divert a portion ofthe cooling airflow from one surface of the circuit board to an oppositesurface of the circuit board (step 2708). This method may be extended todesign offsets for a plurality of elongated guides for a systemcontaining a plurality of circuit boards.

[0111] The invention disclosed herein is susceptible to variousmodifications and alternative forms. Specific embodiments therefore havebeen shown by way of example in the drawings and detailed description.It should be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, the invention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the present invention as defined by the claims.

1. A structure for removably attaching a circuit board within a housing,wherein the housing includes a pair of slots disposed therein uponopposite inner surfaces of the housing, and wherein a cooling airflow isproduced within the housing, the structure comprising: a pair ofelongated guides, a first elongated guide of the pair of elongatedguides affixed to a first side of the circuit board and a secondelongated guide of the pair of elongated guides affixed to a second sideof the circuit board that is opposite the first side of the circuitboard; wherein each of the elongated guides includes a first portionthat slidingly engages a corresponding slot of the pair of slots whenthe circuit board resides within the housing and a second portion thatis affixed to the circuit board; and wherein the second portion of eachelongated guide is offset from the first portion of the elongated guideto alter the cooling airflow within the housing to selectively divert aportion of the cooling airflow from one surface of the circuit board toan opposite surface of the circuit board.
 2. The structure of claim 1,wherein: a first plurality of components reside upon a first surface ofthe circuit board and produce a first heating amount; a second pluralityof components reside upon a second surface of the circuit board andproduce a second heating amount; and the offset of the second portionsof the guides from the first portions of guides divides the coolingairflow into a first cooling airflow volume that is adequate todissipate the first heating amount and a second cooling airflow volumethat is adequate to dissipate the second heating amount.
 3. Thestructure of claim 1, wherein the first portions of the guides couple tosecond portions of the guides via rounded connecting portions thatprovide a smooth transition to minimize the disruption of airflow. 4.The structure of claim 1, further comprising extractors coupled to theguides that removably attach the circuit board to the housing.
 5. Thestructure of claim 1, wherein the circuit board comprises: a motherboard affixed to the pair of guides; and at least one daughter boardremovably attached to the motherboard.
 6. The structure of claim 5,further comprising: mother board extractors pivotally coupled to thefirst portion of the elongated guides and that removably attach thecircuit board within the housing; and daughter board extractorspivotally coupled to the second portion of the elongated guides and thatremovably attach the daughter board to the motherboard.
 7. The structureof claim 6, wherein the daughter board and the motherboard are co-planerwhen coupled.
 8. The structure of claim 6, wherein the mother boardextractors cannot be disengaged from the housing unless the daughterboard has been removed from the motherboard.
 9. The structure of claim6, wherein: the pair of slots disposed therein upon opposite innersurfaces of the housing reside in a slot plane; and when the motherboardresides within the housing, a plane of the motherboard does not coexistwith the slot plane.
 10. The structure of claim 9, wherein an offsetbetween the slot plane and the plane of the motherboard is selected todivert a chosen airflow volume.
 11. A structure for housing a pluralityof electronic components that are intercoupled to supportcommunications, the structure comprising: a housing that is adapted toreceive a plurality of circuit boards; a cooling fan module thatproduces a cooling airflow within the housing; a pair of slots disposedwithin the housing to receive a circuit board; and a circuit boardincluding: a first plurality of components that reside upon a firstsurface of the circuit board and that produce a first heating amount; asecond plurality of components reside that upon a second surface of thecircuit board and that produce a second heating amount; a pair ofelongated guides, a first elongated guide of the pair of elongatedguides affixed to a first side of the circuit board and a secondelongated guide of the pair of elongated guides affixed to a second sideof the circuit board that is opposite the first side of the circuitboard; wherein each of the elongated guides includes a first portionthat slidingly engages a corresponding slot of the pair of slots whenthe circuit board resides within the housing and a second portion thatis affixed to the circuit board; and wherein the second portion of eachelongated guide is offset from the first portion of the elongated guideto divide the cooling airflow into a first flow volume that is adequateto dissipate the first heating amount and a second flow volume that isadequate to dissipate the second heating amount.
 12. The structure ofclaim 11, wherein the first portions of the guides couple to secondportions of the guides via rounded connecting portions that provide asmooth transition to minimize the disruption of airflow.
 13. Thestructure of claim 11, further comprising extractors coupled to theguides that removably attach the circuit board to the housing.
 14. Thestructure of claim 11, wherein the circuit board comprises: a motherboard affixed to the pair of guides; and at least one daughter boardremovably attached to the motherboard.
 15. The structure of claim 14,further comprising: mother board extractors pivotally coupled to thefirst portion of the elongated guides and that removably attach thecircuit board within the housing; and daughter board extractorspivotally coupled to the second portion of the elongated guides and thatremovably attach the daughter board to the motherboard.
 16. Thestructure of claim 15, wherein the daughter board and the motherboardare co-planer when coupled.
 17. The structure of claim 15, wherein themother board extractors cannot be disengaged from the housing unless thedaughter board has been removed from the motherboard.
 18. The structureof claim 15, wherein: the pair of slots disposed therein upon oppositeinner surfaces of the housing reside in a slot plane; and when themotherboard resides within the housing, a plane of the motherboard doesnot coexist with the slot plane.
 19. The structure of claim 18, whereinan offset between the slot plane and the plane of the motherboard isselected to divert a chosen airflow volume.
 20. A structure for housinga plurality of electronic components that are intercoupled to supportcommunications, the structure comprising: a housing that is adapted toreceive a plurality of circuit boards; a cooling fan module thatproduces a cooling airflow within the housing; two pairs of slotsdisposed within the housing substantially equidistant from the housingwalls, the two pairs of stocks to receive a pair of circuit boards; anda pair of circuit boards, each of the circuit boards including: a firstplurality of components that reside upon a first surface of the circuitboard and that produce a first heating amount; a second plurality ofcomponents reside that upon a second surface of the circuit board andthat produce a second heating amount; a pair of elongated guides, afirst elongated guide of the pair of elongated guides affixed to a firstside of the circuit board and a second elongated guide of the pair ofelongated guides affixed to a second side of the circuit board that isopposite the first side of the circuit board; wherein each of theelongated guides includes a first portion that slidingly engages acorresponding slot of the pair of two pairs of slots when the circuitboard resides within the housing and a second portion that is affixed tothe circuit board; and wherein the second portion of each elongatedguide is offset from the first portion of the elongated guide to dividecooling airflow into a first flow volume that is adequate to dissipatethe first heating amount and a second flow volume that is adequate todissipate the second heating amount.
 21. The structure of claim 20,wherein the first portions of the guides couple to second portions ofthe guides via rounded connecting portions that provide a smoothtransition to minimize the disruption of airflow.
 22. The structure ofclaim 20, wherein: the housing includes a circuit board volume in whichthe pair of circuit boards reside; the pair of circuit boards divide thecircuit board volume into an upper volume, a middle volume, and a lowervolume; the upper volume includes a plurality of components that resideon an upper surface of an upper circuit board of the pair of circuitboards; the middle volume includes a plurality of components that resideon a lower surface of the upper circuit board and a plurality ofcomponents that reside on an upper surface of a lower circuit board ofthe pair of circuit boards; the lower volume includes a plurality ofcomponents that reside on a lower surface of the lower circuit board;and the offset of the elongated guides of the upper circuit board andthe lower circuit board are selected to adequately cool the uppervolume, the middle volume, and the lower volume.
 23. A method ofdesigning a pair of elongated guides that affix to a circuit board andthat allow the circuit board to be slidingly engaged within anenclosure, the enclosure having a cooling airflow and a pair of slotassemblies, the method comprising: determining a division of the coolingairflow volume within the enclosure by the location of the pair of slotassemblies; determining a first heating amount produced by a firstplurality of components residing upon a first surface of the circuitboard; determining a second heating amount produced by a secondplurality of components residing upon a second surface of the circuitboard; and determining an offset of second portions of the elongatedguides from first portions of the elongated guides to selectively diverta portion of the cooling airflow from one surface of the circuit boardto an opposite surface of the circuit board.